1. Field of the Invention
The present invention relates to a refrigerator, more particularly, to a control method of defrosting operation of a refrigerator.
2. Description of the Prior Art
A cooling process of a conventional refrigerator shown in FIG. 1, is described below. At first, a cooling agent is turned into air of high temperature and high pressure by a compressor (10), subsequently into liquid with low temperature and high pressure through heat transmission with outdoor air in a condenser (12), and finally into transient liquid with low temperature and low pressure for easy evaporation while passing through a capillary tube to flow into a vaporizer or evaporator (14).
The cooling agent of transient liquid enables air in the refrigerator to be cooled or heat-exchanged by evaporation while passing through several pipes of the vaporizer (14), and the cooling agent of vapor with low temperature and low pressure is infused into the compressor (10) for further circulation, where the cooling cycle of the refrigerator is repeated.
The cooled vapor heat-exchanged at the vaporizer (14) is forcibly blown into a freezing chamber (18) and a refrigerating chamber (20) by a ventilating fan (16), so that food in a refrigerator can be kept fresh. A refrigerator damper (22) disposed in the route of the blown cooled vapor keeps the refrigerating chamber (20) at a preset constant temperature (commonly around +3.degree. C.), by controlling supply of cooled vapor from the vaporizer (14).
Frequent opening of a refrigerator door causes inflow of outdoor air, resulting in the formation of frost on the surface of the vaporizer(14) which has to be defrosted by a defroster (24). FIG. 2 is a flowchart illustrating a defrosting operation in the refrigerator. Defrosting operation of the conventional art is described in detail with reference to FIGS. 1 and 2. Table 1 shows a defrosting period of the refrigerator depending on the temperature of outdoor air detected by the outdoor temperature sensor and the number of the uses, i.e., opening and closing use of the refrigerator door in the conventional art.
TABLE 1 ______________________________________ Defrosting period depending on each defrosting temperature mode and the number of the uses of the refrigerator door defrosting mode low temperature high temperature mode (under normal mode mode (35.degree. C. # -50.degree. C. or (20.degree. C. to 50.degree. C. of uses of door -50.degree. C. to +20.degree. C.) to 35.degree. C.) or over 50.degree. C.) ______________________________________ 2 16 hours 16 hours 12 hours 3-4 16 hours 12 hours 12 hours 5 12 hours 12 hours 6 hours ______________________________________
In the cooling process of the refrigerator, the temperature of the outside air is detected by an outdoor air temperature sensor. In case the outdoor temperature is over 50.degree. C. or under -50.degree. C., a controller determines the outdoor air temperature sensor as defective and selects the high temperature defrosting mode (steps 310, 312, 314 for the former, and steps 316, 318, 320 for the latter respectively).
When the temperature is detected between 35.degree. C. and 50.degree. C., and between -50.degree. C. and 20.degree. C. by the outdoor air temperature sensor, the high temperature defrosting mode and the low temperature defrosting mode are selected respectively (steps 322, 314 for the first, and steps 322, 324, 320 for the latter respectively). Temperature is detected between 20.degree. C. and 35.degree. C., the controller selects the normal defrosting mode (steps 324, 326).
The controller counts the number of uses of the refrigerator door for a certain period of time (1 hour as recommendable) with a door detecting switch (step 328), and selects the defrosting period correspondingly as in Table 1 (step 330). The controller generates a signal for defrosting operation of the refrigerator according to the selected defrosting period, and thereby the defrosting heater is operated to remove frost on the vaporizer (14) (step 332).
For instance, if temperature detected by the outdoor temperature sensor is between 20.degree. C. and 35.degree. C., the controller selects the normal defrosting mode, selects a defrosting period depending on the counted number of uses of the refrigerator door, and sends a corresponding defrosting signal. Accordingly frost on the vaporizer (14) is removed by the defrosting heater (24).
When the temperature is over 50.degree. C. or under -50.degree. C., in the same manner as described above, the controller determines the outdoor air temperature sensor defective, respectively selects the high temperature defrosting mode or the low temperature defrosting mode, and selects the corresponding defrosting period depending on the number of uses of the refrigerator door.
In case the defrosting mode is selected at the high temperature mode or at the low temperature mode due to the defective outdoor air temperature sensor, the defrosting period of the refrigerator is selected not by actual outdoor air temperature, therefore resulting in weakening of cooling capability or high consumption of electricity.
If the number of the uses of the refrigerator door is over 5 at the low temperature mode, for example, the given defrosting period is 12 hours. However if, the actual outdoor air temperature were between 35.degree. C. and 50.degree. C., so the defrosting period should instead have been 6 hours. As a result, weakening of cooling capability is caused by the difference of the two defrosting periods.
By way of another example, when the detected outdoor air temperature is over 35.degree. C., thereby setting the defrosting mode at the high temperature mode and the number of use of the refrigerator door is under 2, the given defrosting period is 12 hours. However if, the actual outdoor temperature were under 20.degree. C., the defrosting period should instead have been 16 hours. In this case, excessive consumption of electricity results from higher defrosting frequency.
It is an object of the present invention to solve the problems, weakening of the cooling capability and excessive consumption of electricity as described above, by providing a control method of defrosting period of a refrigerator according to the preset defrosting period in case the outdoor air temperature sensor is defective.